Apparatus for drying materials, especially leather, by means of gases



I. L. FAIRRIE.

APPARATUS FOR DRYING MATERIALS, ESPECIALLY LEATHER, BY MEANS OF GASES.

APPLICATION FILED NOV- 6. I920.

Patented Mar. 8, 1921.

UNITED STATES PATENT ()FFHCE.

JAMES LESLIE FAIRRIE, 0F LIVEBIQOL, ENGLAND.

AIIQABAIUS FOB DRYING MATERIALS, ESPECIALLY LEATHER, BY MEANS OF GASES,

Specification of Letters latent.

Patented Mar. 8, 1921.

Application filed November 6, 1920. .Serial No. 422,298.

To all whom it may concern I Be it known that 1, JAMES LESLIE FAIRRIE, subject of the King of Great Britain, residing in Liverpool, in the count of Lancaster and Kingdom of England, ave invented certain new and useful Improved Apparatus for Drying Materials, Especially Leather, by Means of Gases, of which the following is a specification.

This invention relates to an improved process and apparatus for dr ing materials especially organic materials aving an organized structure 6. g. leather, or wood by means of gases, especially by heated atmospheric air.

Drying leather is a particularly dchcate operation because while it is desiredto effect drying in the minimum time, it is also necessary to prevent injury to the material or deterioration of the material. In the first place there is a temperature which it is desirable not to exceed throughout the operations, and in the second place it appears to be undesirable to remove the moisture from the surface layer more rapidly than moistime can be supplied from the under-lying layers probably by capillary action; it therefore the air which is used is too the moisture is evaporated from the surface too rapidly and this surface deteriorates by becoming hardened. These difiiculties are experienced particularly in the case of heavy leather, and the present invention aims especially at overcoming these difliculties in this case, but the invention is not limited thereto, since it may be applied to any type of drying in which it is desired to maintain constant conditions of humidity and preferabl of temperature also.

c this end the invention consists in a drier having a hygrometer or equivalent, and means controlled thereby for adjusting the humidity of the gas entering the drier, preferably by varying the relative proportion of atmospheric air and air leavlng the drier and by-passed back to mingle with the atmospheric ail entering the drier. The invention further consists in a drier provided with a Wet-bulb thermometer and a relay or equivalent controlled thereby and adapted to add moisture to the air entering the drier to maintain a constant humidity at constant (dry-bulb) temperature. The invention further consists in a drier maintained at constant (dry-bulb) temperature dry,

and having a wet-bulb thermometer operating a relay which controls a valve to vary the relative proportions of atmospheric air and air leaving the drier to make a mixture of constant humidity to enter the drier.

The 1nvention further consists in a drier havin means for positively controlling the humi ity of the entering air as above described in combination with a dry-bulb thermometer or equivalent, and means to regu-. late the temperature of the gas which means may consist of adjustable steam heaters, for instance a plurality of steam valves may be employed each of which may be adjustable rough y, by hand and controlled by a thermostatic controlling device operated on the gust principle 2'. e. to out off the steam absolutely or to leave it full on in accordance with the control of a relay actuated by the thermometer.

A preferred form of the apparatus is shown in the accompanying drawings in which A Figure 1 is an elevation,

2 is a plan,

Fig. 3 is a cross section, v

Fig. 4 is a'detail of the slide valve.

Fig. 5 is a detail View showing the thermostatic means of controllin the air heater.

In these drawings a: is a c amber to contain the hides, carried by a boge This chamber may be in the form 0 a tunnel through which atmospheric air may be blown by means of a fan or blower a, having a fresh air inlet d. The path of therelatively dry air is shown by single arrows. Thus air is maintained at constant humidity as hereafter described. The path of the moist air leaving the hides or the like is shown by double arrows. Thus air passes from the tunnel ac to the conduit 2. Part of this moist air is by-passed through the fan and the mixture of moist air from c and atmospheric air from (Z enters the tunnel from the conduit f after passing through the thermostatic steam heater 0 which may be of any known type, c. g. the usual kind operated on the gust principle in which steam is allowed to flow into the heater in gusts under control of the thermostatic device in accordance with the temperature variations of the air. In Fig. 5 is shown in detail the device for controlling this steam supply to the heater through the in. tervention ofthe dry bulb thermometer m.

In this figure 41 are the electric connections leading to the relay 42. 43 are the supply mains and 44 is the circuit operating the solenoid 45 which raises the valve 47 by the stem 46 forming a part thereof, thereby cutting oif the steam-supply from steam-pipe 48 to the pipe 49 leading to the air-heater c. This solenoid comes into operation when the temperature rises above a given point, thereby cutting ofl". the steam. As soon thereafter as the temperature again falls below the determined maximum, the circuit of the solenoid is broken, the valve drops,-and steam is again admitted from pilpe 48 to the heater 0 through the pipe 49. ig. 4 shows a detailof the slide valve 6 which is raised and apparatus it is lowered by the guide In. The guide is is in the form of a rod which passes through the interior of the solenoid is, arranged in the electric circuit 2, which circuit is adapted to be opened or closed by the wet bulb thermometer n, as indicated in said Fig, 4, thereby energizing the solenoid and movlng the rod to lower or raise the slide valve 6, as will be readily understood. Thereby, when the thermometer n falls, the moist air sup- .ply to the air current passing into the drier 18 cutoff or diminished and when it rlses, it is restored of increase Dry air enters at g, and moist air enters at '7' either from the tunnel as above described or from any other source.

The air of constant humidit leaves at h. The moist air exhaust is at This slide valve is not an essential feature of the arrangement as moisture can be added to the air in any suitable manner provided this is under the control of the hygrometer. Fig.

1 shows a dry-bulb thermometer m control.

ling the heater and a wet bulb thermometer n controlling the slide valve through any suitable relay devices acting onk.

The steam heater valves may be adjusted roughly by hand.

It Will be seen thatin the above described ture and humi it manner. The pre etermined humidity must ss'ible to fix the temperabe at least equal to the maximum humidity of the atmospheric air during the period within which the adjustment is not altered,

unless .of course drying means are provided for the gases prior to entering. the drier.

It may be interpolated here that the above mentioned method of humidity control aplies also to. cases-in which dr air is used, ut as in such cases it is easier to obtain constant humidity, the invention finds its primary application in cases when ordinary in a very satisfactory I nesses.

atmospheric air is employed as the gas enters the drier.

.It will be understood of course that the adjustment of the relay devices operated by the dry-bulb and Wet-bulb thermometers may be altered either week by week or da by day or even oftener if desired in accor ance with changing atmospheric conditions or otherwise.

Clearly when a wet-bulb thermometer is employed, it is also necessary to maintain a constant dry-bulb temperature if a constant humidity is to be'maintained by constancy of the wet-bulb temperature.

, I declare that what I claim is 1. In a drier, means to maintain constant (dry-bulb) temperature, a wet-bulb thermometer adapted to cpntrol a valve to vary the relative proportions of atmospheric air and moist air'to make a mixture of constant humidity to enter the drier;

. 2. A drier having a hygrometer and means controlled thereby for adjusting the humidity of the .gas entering the drier ineluding means for by-passing part of the moist air leaving the drier to mingle with the atmospheric air entering the drler.

3. In a drier, means for passing an aircurrent through the drying chamber, means for heating said air to a fixed temperature, and a duct for carrying ofi' the moist air from the said drying chamber, in combination with means for causing moist air from. said duct to flow into said air-current, a wet bulb thermometer arranged in the air current and connections between. the same and the means for causing the moist air to flow into the air current, whereb the wet bulb thermometer alone controls t e latter.

4. In adrier, means forpassin an air current through a drying chain er and means for"maintain'ing the heat of said air current at a fixed tem erature, in. combination with 'awet bulb thermometerarranged in contact with the air in the drying chamber, and means for introducing moist air into the air current before'entering the drying chamber and connections between the wet-bulb thermometer and the moist-air introducin means to control the latter from the wet 'ulb thermometer. 1

In witness whereof, I have hereunto signed 111 name this 25th da of October, 1920, in tile presence of two subscribing Wit- JAMES LESLIE FAIRRIE. Witnesses:

DOROTHY GRAY,

JOHN MCLACHLAN. 

